SHE AIN’T HEAVY: Eli Manning gives a lift to his 16-month-old daughter, Ava, during a recent trip to Citi Field. Photo: Bill Kostroun

It was a snapshot, no more than that, but the one taken in The Bronx last night served to validate general manager Brian Cashman’s decision at the July 31 trade deadline to stand pat with his pitching staff rather than deal even second-tier prospects for a veteran rental such as Ryan Dempster.

When the Yankees found themselves in a stop-gap mode because of the left elbow inflammation that has sent CC Sabathia to the disabled list until at least Aug. 24, the team turned to 25-year-old David Phelps against Texas in the first game of a seven-game homestand that features four against the Rangers before three against the Red Sox.

And in a splendid bit of serendipity, Phelps was opposed by Dempster, the veteran who had struggled in his first two starts following his acquisition from the Cubs and continued to do so last night, battered for eight runs on nine hits in six innings of the Yankees’ 8-2 victory that lifted the Bombers a half-game ahead of Texas for the AL’s best record and top playoff seed.

That makes for 16 earned runs on 24 hits in 17 1/3 innings for an 8.31 ERA in Dempster’s three starts for Texas if you’re scoring at home, as the Yankees did so often last night and as Rangers’ CEO Nolan Ryan presumably is as well.

Cashman has taken to bargain-hunting the last few seasons, one eye on the budget, the other on his own farm system. When there is doubt, the benefit invariably goes to the kids.

And so it was that the precocious Phelps, rather than the 35-year-old Dempster, was given the ball last night by manager Joe Girardi, whose team has thrived despite a large number of significant injuries across the roster; so it was that Phelps was the understudy for Sabathia, who is merely the soul of the rotation.

“Those are very big shoes to fill,” Phelps said after using his off-speed pitches to advantage in getting the victory by allowing two runs in five innings, the first time he’s gone that far in four starts. “What [Sabathia] brings in terms of stability, he’s been the anchor of the staff the entire time he’s been here.

“For me to give the team the chance to win in his spot is huge. Hopefully I can keep doing it.”

Phelps, a 14th-round selection in the 2008 draft, in his third tour of duty this season with the Yankees, having worked primarily out of the bullpen. He would be on schedule to start Saturday against the Red Sox before Sabathia is expected to reclaim his spot by starting in Cleveland on Aug. 24, the day he is due to come off the DL.

“We’ve seen him grow up a lot since spring training in 2011,” manager Joe Girardi said of Phelps, who needed 26 pitches to get through the first inning in which he allowed one run and surrendered a second-inning leadoff home run. He then shut the door before exiting after the fifth, turning the game over to Derek Lowe.

“So it’s not really a surprise with the way he’s gone about his business in spring training up through now.”

And it’s no longer a surprise when a stop-gap seamlessly fills a Pinstriped role. The rotation might lack panache — certainly with Andy Pettitte sidelined — but the starters have been especially effective, recording the fifth-best ERA in the AL (4.05), while producing the second-most innings per start in the league (just under 6 1/3) after ranking between eighth-and-12th in that category every year since 2004.

Indeed, the Yankees went 12-6 when Sabathia was on the DL with a groin strain from June 25 through July 16.

“Any time you lose a guy like CC it’s going to be tough, but it gives someone else the opportunity to go out and do the job,” said Russell Martin. “Every time this year, whether it’s been a pitcher or a guy off the bench, that guy has taken advantage of the opportunity.”

Last night, pitching in Sabathia’s spot and against Dempster, Phelps took advantage of the opportunity. It was a feel-good night in The Bronx, on the field and in the executive suite.